Lubricant



Patented June 3, 1947 LUBRICANT James F. Cook, Albany, Califi, assignorto Union Oil Company of California, Los Angeles, Calif., a corporationof California No Drawing. Application January 19, 1945, Serial No.573,629

6 Claims.

1 This invention relates to lubricants and more particularly to filledlubricants having extreme pressure characteristics prepared by theaddition to ordinary lubricating oils and. greases of solid fillers ashereinafter disclosed, which fillers have the effect of minimizingfriction and reducing bearing wear even under heavy duty conditions.

The advantage accruing from the use of certain solid type additives inlubricating oils and greases has long been recognized in the art. Theliterature contains references to a wide variety of fillers which may beclassified according to their apparent function as follows:

1. Those materials which are in themselves lubricants in the dry stateand merely enhance the lubricating qualities of the grease, or areintended to remain after the grease has been volatilized by thetemperature of operation. Into this class would be placed for examplegraphite and mica, both of which materials have been known and used formany years.

2. Those materials which fill unevenness in the rough bearing and thuslower friction by exposing a smoother, padded bearing surface. Thisclass seems most applicable to large, slow-speed, lowpressure bearingswhere abrasion is very apt to be a serious problem and in this categorywould be placed such fillers as asbestos fiber, wood flour, wool yarn,fish scales, charcoal, and the like.

3. Thosematerials which exert a polishing ac- 1.

tion and find application by virtue of their ability to abrade thesurfaces yielding as a result a smoother bearing. Such fillers seem tobe of more value in high-speed, low-load bearings where high frictionalheat, due to rough bearings is a predominate factor. This class appearsdefinitely detrimental when a heavy load with resultant extremepressures is applied. Under such conditions of high load abrasion of thehearing becomes excessive and it very rapidly disappears. Materialsshowing this abrading and polishing action, for example, are emery dust,

zinc oxide, alum, red lead, iron filings, landthe like.

2 and borates to exert the necessary surface action of such a naturethat they may be rightly classified in :this group 4.

It should be pointed out that distinction between classes 3 and 4 isextremely difficult without actual test, as materials which might beassumed to be abrasive are found to exhibit unusual surface activeproperties. In such cases particle size would of course be of extremeimportance.

It is an object of my invention to provide a novel class of solidmaterials which may be added to lubricating oils and greases to giveimproved filled lubricants having extreme pressure properties. I

It is a more particular object of my invention to provide a class offillers for lubricating greases falling in the fourth class of the abovecategories exerting a beneficial effect because of surface activeproperties.

It is another object of my invention to prepare a lubricant which by theaddition thereto of fillers as hereinafter disclosed has improvedextreme pressure characteristics.

More specifically it is an object of my invention to prepare, alubricant having improved extreme pressure characteristics by theaddition thereto of -inor amounts of the fillers according to thisinvention which fillers do not cause the breakdown of the greasestructure in operation and which do not function as abrasives towardsthe bearings in which they come in contact.

Other objects and advantages of my invention will become apparent tothose skilled in the art as the description thereof proceeds.

I have found that the incorporation of a small portion of a finelypowdered, non-crystalline metallic sulfide materially enhances thebearingwear characteristics and the load-carrying capacity of a normalgrease.

More specifically I have found that the higher sulfides, providing theyare non-crystalline, of metals capable of uniting with sulfur in morethan one ratio are highly active in preventing failure of a heavilyloaded bearing. Included in this classification are such metallicsulfides as antimony pentasulfide, arsenic pentasulfide, bariumtrisulfide, ferric sulfide, selenium sulfide, sodium monosulfide, sodiumpentasulfide, chromium sulfide,mercuric sulfidamolybdenum tetrasulfide,and the like. The non-crystalline sulfides of the polyvalent metals arethe preferred class of compounds and more particularly antimonypentasulfide, mercuric sulfide and stannic sulfide. I have also foundthat certain metallic sulfides such as for example zinc sulfide, andmercurous sulfide may be prepared in either crystalline or amorphousform and in the latter instance are desirable as fillers for lubricantsaccording to my invention.

n the basis of numerous tests I have found certain restrictions andconditions which must be taken into consideration in the use of thesesulfide type fillers. In addition to the stipulation that they must benon-crystalline and that they preferably are the higher sulfides ofmetals capable of forming compounds with sulfur in more than one ratio,the sulfide must be one which is stable at normal atmospheric conditionsof temperature and of humidity and of such physical state that it may besufficiently finely powdered so that the abrasive action, if any, willnot exceed the action as a surface film producing material. One furtherrestriction in the use of this type of additive is that the greaseshould preferably be one with a high melting point. It must also beremembered that fillers have limitations in regard to applications forwhich they are suitable. Filled greases for example have several typesof functions other than bearing lubrication such as thread compounds,cable'and gear lubricants, and the like.

Itis thought that the activity of the particular sulfides as disclosedabove is due to the thermal and pressure decomposition of the sulfide toliberate elemental sulfur in a highly active form which functions toprovide a sulfide bearing sur face. as in a typical sulfurized extremepressure lubricant. However, I do not wish to limit my invention to anytheory as to the mechanics of their operation.

The testing of the filled greases presents a variety of problems dueprimarily to the Wide range of functions performed by the variousfillers. The following test has been found very useful in segregatingand classifying fillers of class 4 above. A modification of theAlmentest was used in which three instead of the usual two bushings wereemployed. A description of the Almen test apparatus and method ofoperation is included in a paper entitled Extreme Pressure Lubricantspresented by Wolf and Mougey at the thirteenth annual meeting of theAmerican Petroleum Institute at Houston, Texas, on

November 17, 1932. In my modification of this test method two bushingsare located on the under side of the test pin, one at each end, and thethird or load bushing is located on top, straddling the gap formed bythe lower bushings.

Whereas, the cup on the Almen test is designed for use with aliquid, itwas felt that due to the structure of the greases to be tested an unfaircomparison would be obtained because of the failure of the grease tofeed properly between the bushings if they were arranged according tothe standard method. By use of three bushings, as described above, allparts of the test pin are in contact with a portion of the grease for atleast. one-half of its circumference thus insuring suf cient contact toprovide maximum lubrication. Another modification of the standard testhas been to apply a constant load for a variable time. To date all testshave been made by allowing the bearing to run 30 seconds without loadand subsequently loading the arm at the rate of 2 pounds per secondsuntil an arm load of 8 pounds is reached; and then allowing the test torun either until failure occurs or for a definite period of time, suchas for example two hours. Inthis apparatus each two pound weight is 4equivalent to 1,000 pounds per square inch pro- .l'ected bearing areathus a total of 4,000 pounds per square inch is obtained. Theseconditions for operating the machine appear to give the best correlationwith actual service data on the performance of extreme pressurelubricants.

In general fillers of classes 1 and 2 above fail before the full load isapplied or shortly thereafter, with seizure and shearing of the testpin. Class 3 fillers run for a somewhat greater length of time giving auniform abrasion and polishing of the test piece until the amount ofabraded metal particles becomes great enough to cause scoring withsubsequent seizure and failure. A1- most all pins used in tests withfilled greases using a filler of class 4 have shown a highly uniformpolish at the end of the test, although the lapse of time before seizurevaries over a comparatively wide range.

In one series of tests to determine the relative effectiveness of thevarious fillers a standard light grade of barium soap grease wasemployed having the following composition:

Composition Barium soap Weight, Per Cent 25.00 Free alkali do 0.02 Freefat d0 0.30 Water do 0.20 Glycerin do 0.23 Dye l do 0.005 Mineral oil do74.245 S. U. Vis. at 100 F., secs 440 S. U. Vis. at 130 F., secs 185 S.U. Vis. at 210 R, secs 54 Viscosity index Flash, COC, "F 410 Pour point,F 90 The characteristics of this grease are:

Tests A. S. T. M. unworked pen/77 F 345 A. S. T. M. worked pen/77 F 335A. S. T. M. dropping point, "F 400+ Sulfated ash, percent l2. 5

Employing this grease, numerous tests were made by the above procedureas to the efiectiveness of various metallic sulfide type fillerstogether with other fillers for comparative purposes. The results ofthese tests are given in Table I below:

Filler Pin gi Comments 5:)

Scored and seized. 120 Pin darkened. S5 120 Pin darlcenedgrease darkenedadjacent to pin. 5% Aluminum do 16 Severely scored previous to hydrate.seizure; sheared. 50 5% PbO do 15 Severely scored previous to seizure;sheared. 3% SbzSs Brass--. 120 Pin very black. No sign of scoring. 5%HgS Stee1 70 Slight darkening highly po1ishedslightly scored. 5% SnSz do120 Pin blackhigh1y polished very good.

table. I do not wish to limit myself, however, to these three metallicsulfides but only point out a consistency of the comparison obtainedusing various base greases.

These fillers may be incorporated in the desired greases in a number ofways. In some cases ior example it may be desirable to saturate thefiller with a mineral oil, a fatty oil or a mixture of the two to aid inblending with the grease. However, the addition of the finely powderedmetallic sulfides as hereinbefore disclosed may be made directly to thegrease with means provided for intimately mixing and dispersing saidfillers throughout the body of the grease. Lumpiness or localconcentrations of the sulfide should of course be avoided. Methods ofincorporating such fillers in greases are well known in the art and arenot contemplated by my invention.

My invention is therefore carried into effect by very thoroughly mixingor dispersing in any desirable manner from about one to about tenpercent and preferably from about two to about six per cent of a finelypowdered, non-crystalline metallic sulfide such as antimony pentasulfidein an oil or grease base possessing in itself good lubrieatingqualities. For this purpose any desirable oil or grease may be employed,however, I have shown that the high meltin point non-hydrous greases aresuperior for this purpose to the lower grades of grease.

I do not wish to limit my invention to the use of fillers selectedsolely from the simple non crystalline metallic sulfides inasmuch as Ihave found that thiosalts or complex metal sulfides are excellentfillers for extreme pressure lubricants. Complex zinc-antimony sulfides,such as Zn(SbS2) 2 zinc-tin sulfides and related compounds wherein themetals within the complex may be at different oxidation levels may beemployed.

Whereas, the non-crystalline metal sulfides as hereinbefore disclosedmay be advantageously employed in lubricating oils as well as greases toimpart extreme pressure properties thereto they appear to beparticularly efiective in grease structures and such usage constitutesthe pre ferred embodiment of my invention.

While the preferred extreme pressure additives of me invention have beendescribed, I do not intend to be limited to the specific compoundsmentioned for it is apparent from the foregoing description and examplesthat a new class of fillers for lubricants and particularly forimparting extreme pressure characteristics to said lubricants has beendiscovered and many variations and modifications in the utilization ofthese ma- 6 terials may occur to those skilled in the art withoutdeparting from the spirit and scope of the following claims.

I claim:

1. A composition of matter comprising a lubricant of the classconsisting of oils and greases and a small amount, sufficient to impartextreme pressure properties to said lubricant, of a finely divided,non-crystalline metallic sulfide dispersed therein.

2. A composition of matter as in claim 1 wherein the finely dividednon-crystalline metallic sulfide is selected from the sulfides of thepolyvalent metals.

3. A composition of matter comprising a lubricant of the classconsisting of oils and greases and from about 1% to about 10% of afinely divided, non-crystalline metallic sulfide dispersed therein.

4. A composition of matter comprising a lubricant of the classconsisting of oils and greases and from about 1% to about 10% of finelydivided antimony pentasulfide dispersed therein.

5. A composition of matter comprising a lubricant of the classconsisting of oils and greases and from about 1% to about 10% of finelydivided mercuric sulfide.

6. An extreme pressure lubricant of the class consisting of oils andgreases to which has been added from about 1% to about 10% of finelydivided stannic sulfide.

JAMES F. COOK.

REFERENCES CITED The following'references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 576,307 Gilbert et a1 Feb. 2,1897 2,156,803 Cooper et a1. May 2, 1939 2,290,032 Burk July 14, 19421,957,259 Gallsworthy May 1, 1934 2,195,669 Cavanaugh Apr. 2, 19402,258,309 Zimmer Oct. 7, 1941 2,283,581 Schalzitti May 19, 19422,285,739 Merkle June 9, 1942 2,361,211 Kalischer Oct. 24, 19442,367,946 Kaercher Jan. 23, 1945 FOREIGN PATENTS Number Country Date14,835 Great Britain 1886 OTHER REFERENCES Klemgard, Lubricating Grease,p. 717, pub. 1937 by Reinhold Pub. Corp.

